function wearo_widget_script() {
    if ( is_product() ) {
        echo '<script src="https://wearo.io/widget/tryon-widget.js"></script>';
        echo '<script>TryOnWidget.init({ apiKey: "wearo_xxx", productSelector: ".woocommerce-product-gallery__image img" });</script>';
    }
}
add_action( 'wp_footer', 'wearo_widget_script' );

<script src="https://wearo.io/widget/tryon-widget.js"></script>
<script>
  TryOnWidget.init({
    apiKey: 'wearo_xxxxxxxxxxxxxxxxxxxx',
    productSelector: '.woocommerce-product-gallery__image img',
    brandColor: '#000000'
  });
</script>